The present invention relates to a speed-up spindle unit for connection to main shafts of machine tools, and, more particularly, to a speed-up spindle unit suited for rotating a small diameter cutting tool at high speeds.
Various types of speed-up spindle units have been proposed and, for example a planetary gear mechanism is connected between an input shaft connected to the main shaft of the machine, and a high speed spindle (an output shaft) having a chuck is attached to a forward end of the spindle. The planetary gear mechanism increases the speed of rotation of the input shaft so that the high speed spindle rotates at high speeds.
One of the disadvantages of the speed-up spindle unit having a planetary gear mechanism is relatively low rigidity which is likely to cause vibrations in the working tools. Another disadvantage is that its capacity for carrying loads is small.
Accordingly, an object of the present invention is to provide a speed-up spindle unit having a high rigidity structure.
Another object of the present invention is to provide a speed-up spindle unit having a torque transmitting stability.